Hi this is my first post on this forum, so thanks for inviting me in.
I am experimenting with making a large diaphragm (50mm) true capacitor (condenser) microphone using just a diaphragm and back plate mounted into an insulated housing that I will place in a mesh Faraday cage for noise reduction along with a pre amp that I need some help with please.
My aim isn't to construct something better or even as good as something than I could buy, but more to see if I can actually machine ( I have a lathe) something accurately enough that would work of sorts, bearing in mind I will need to keep the air gap separation between diaphragm and back plate as small as possible and work with some pretty thin splattered mylar materials for the diaphragm.
If you like it's a mix of an electrical and a mechanical engineering challenge.
Most of my research leads me to electret microphone circuits, which this is not as I am just using a simple two plate construction.
I know I will need to generate a bias voltage for the capacitor plates and plan to produce this using small 3v button cells in series to generate my 48V, which seems to be a standard voltage used on condenser microphones and phantom supplies. Using batteries and having them located right at the capacitor plates should keep noise to a minimum. Current drain should also be minimal as I am just using it to polarise the plates of the capacitor.
I don't really know what size of usable signal I will be able to generate but I suspect it will be small and of a high impedance.
I don't want to go and buy a pre amp ready made as that would be cheating and I won't learn much, so I was thinking of using a three op amp instrumentation amplifier to give me the high to low impedance conversion but not sure if is this is a good idea or not. Maybe just a FET input stage would be sufficient. Any recommendations on a practical design from someone that has trod a similar path as opposed to a theoretical one and how I could couple the two plate mic to the pre amp would be greatly appreciated.
Many Thanks
I am experimenting with making a large diaphragm (50mm) true capacitor (condenser) microphone using just a diaphragm and back plate mounted into an insulated housing that I will place in a mesh Faraday cage for noise reduction along with a pre amp that I need some help with please.
My aim isn't to construct something better or even as good as something than I could buy, but more to see if I can actually machine ( I have a lathe) something accurately enough that would work of sorts, bearing in mind I will need to keep the air gap separation between diaphragm and back plate as small as possible and work with some pretty thin splattered mylar materials for the diaphragm.
If you like it's a mix of an electrical and a mechanical engineering challenge.
Most of my research leads me to electret microphone circuits, which this is not as I am just using a simple two plate construction.
I know I will need to generate a bias voltage for the capacitor plates and plan to produce this using small 3v button cells in series to generate my 48V, which seems to be a standard voltage used on condenser microphones and phantom supplies. Using batteries and having them located right at the capacitor plates should keep noise to a minimum. Current drain should also be minimal as I am just using it to polarise the plates of the capacitor.
I don't really know what size of usable signal I will be able to generate but I suspect it will be small and of a high impedance.
I don't want to go and buy a pre amp ready made as that would be cheating and I won't learn much, so I was thinking of using a three op amp instrumentation amplifier to give me the high to low impedance conversion but not sure if is this is a good idea or not. Maybe just a FET input stage would be sufficient. Any recommendations on a practical design from someone that has trod a similar path as opposed to a theoretical one and how I could couple the two plate mic to the pre amp would be greatly appreciated.
Many Thanks